Blizzard’s Hearthstone: Heroes of Warcraft collectible card game has focused so far on pitting players against one another in free-to-play online battles, but it’s about to expand into a single-player adventure — as long as you can pay the entry fee.

We’ve known that Hearthstone’s first major expansion, Curse of Naxxramas, was coming this summer for quite some time, but Blizzard is finally detailing how you can buy it. The developer plans to dole out each part of the five-section dungeon one week at a time. The good news is that the first “wing” of the dungeon, Arachnid Quarter, is free during Hearthstone’s Curse of Naxxramas launch event. Blizzard says it plans to run that event for a month.

That brings us to how much it will cost to get you all five parts of the expansion. It’s pretty confusing, so stick with us:

You can get the entirety of Curse of Naxxramas at any time for $25.

But if you get the first part free during the launch event, you can get the remaining four for $20.

If you buy a wing of Naxxramas individually, it will cost $7 or 700 gold.

If you own the first two parts, you can buy the rest in a bundle for $15.

If you own the first three parts, you can buy the rest in a bundle for $10.

If you buy the bundle, you’ll still have to wait for Blizzard’s release schedule — so don’t think you’ll get to play all five parts of the expansion one after the other on day one if you drop the $20.

Hearthstone is Blizzard’s first major free-to-play game as well as its first mobile game. The developer spent the last decade dominating the massively multiplayer online sector with World of Warcraft, and now Hearthstone is showing that the studio can work with in-app purchases and tablets as well. The game came out of beta and hit iOS earlier this year. Hearthstone is the 25th highest-grossing game on iPad in the U.S. right now.